The idea that the Civil War was a vanguard-led "war of liberation" to free the slaves is very Marxist. That thesis and its propagation is the agenda.
Moreover, inculpation of the South's Lost Cause, to darken modern Southerners morally -- this is the game Transactional Analysis calls "Blemish" -- and discredit them before the rest of the nation is a talisman of left-wing politics and front-building.
Wait for it, and rely on it, that McPherson will produce a book about Reconstruction and Jim Crow. Maybe two.
I too am in full accord with those who fought hold the Union, together along with dismantling the slave empire, which locally would have freed the slaves.
Not taking the pro-Confederate, pro-slavery side during the Civil War does not make one a commie loving Marxist swine.
Reconstruction and the Jim Crow period are valid subjects which should not be swept under the rug.